P1308PHOSPHATE-LOWERING USING SUCROFERRIC OXYHYDROXIDE: CALCIFICATION PROPENSITY (T50) IN HEMODIALYSIS PATIENTS. POST-HOC ANALYSES OF A RANDOMIZED, CONTROLLED CLINICAL TRIAL

Abstract Background and Aims Lowering serum phosphate with sucroferric oxyhydroxide (SO) therapy reduces calcification propensity (measured with the T50 test) in hemodialysis patients (Cejka et al. Abstract FR-PO149, ASN Kidney Week 2019). Intriguingly, we observed considerable inter-patient variability for changes in T50 in response to SO treatment, despite similar reductions in serum phosphate. Method Post-hoc analysis of a randomized, controlled cross-over study investigating the effects of serum phosphate lowering using oral phosphate binder therapy with SO on calcification propensity (T50). Patients with changes of serum phosphate of approximately -0.5 mmol/l between phosphate binder wash-out and high dose (2000 mg/d) SO and were selected and classified as “responders” (showing profound changes in T50) and “non-responders” (showing very little change in T50). Data are shown as means ± SD. Results “Responders” (N=4) and “non-responders” (N=4) showed similar degrees of lowering of serum phosphate with high-dose SO treatment (-0.47 ± 0.06 vs. -0.49 ± 0.01 mmol/l). “Responders” showed marked increases in T50 (+108 ± 26 min), but “non-responders” did not (+6 ± 24 min). When comparing other laboratory parameters during the wash-out phase between “responders” and “non-responders”, no obvious difference in single parameters or pattern of laboratory parameters was apparent for ionized calcium (1.11 ± 0.1 vs. 1.01 ± 0.1 mmol/l), phosphate (1.76 ± 0.31 vs. 2.06 ± 0.47 mmol/l), T50 (285 ± 82 vs 271 ± 38 min), albumin (3.9 ± 0.2 vs. 4.1 ± 0.4 g/dl), magnesium (1.07 ± 0.17 vs. 0.98 ± 0.14 mmol/l), bicarbonate (22.0 ± 3.6 vs. 24.1 ± 3.0 mmol/l), iPTH (301 ± 156 vs. 463 ± 303 pg/dl) or iFGF23 (6903 ± 9480 vs. 1097 ± 927 pg/ml). Conclusion Similar degrees of phosphate lowering do not lead to a similar improvements in T50. T50 “responders” versus “non-responders” cannot be identified using current standard laboratory parameters.